I want to get a new MBA, I'm still using a mid-2009. I love the protection my Zagg skin has provided, but they cannot confirm that the 2012 skin will work on the 2013 MBA. Were there any external changes to the MBA between 2012 and 2013?

There is an extra hole for a extra microphone on the side, no? It probably doesn't matter with a skin though if it doesn't go up the side.

You are absolutely correct. I now remember reading about the extra mic hole being the only physical external difference. If I remember I will look at a MacBook Air this afternoon. I know we haven't heard any complaints regarding The old Speck case on new 2013 Airs but perhaps people haven't been using the mic (or they are only getting mono input).

Regarding a Zagg skin. All you would have to do is poke or cut a small hole in the skin for allow the mic to work. That's if it even covers the side.